Dear Colleagues, the following code fails assertion (luafont.c, line 1950). But it is enough to transpone last two lines of lua code to avoid it. Could someone explain why the order of node linking matters here? \nokerns=1 \noligs=1 \setbox100=\hbox{ab\-xx} \directlua{% here we move glyph b into disc node local a = tex.box[100].list % glyph a local b = a.next % glyph b local d = b.next % discretionary local _ = d.pre % prebreak dash a.next = d d.prev = a % couple glyph a with disc d.pre = b % let glyph b be prebreak b.next = _ _.prev = b % couple glyph b with dash } \hsize0pt \overfullrule0pt \hfuzz\maxdimen % force hyphenation \unhbox100 % flush the list \end Apparently the assigment discretionary.pre = someglyph someglyph.next = someother and someglyph.next = someother discretionary.pre = someglyph is not the same. Why? Warm greets to u all, Paweł -- Pawe/l Jackowski P.Jackowski@gust.org.pl